1. Field of the Invention
The present invention generally relates to electronic circuits and, more specifically, to the transmission of digital data in a master-slave system. The present invention more specifically applies to communications over a so-called open-drain or open-collector bus (according to the MOS or bipolar technology) and according to a protocol where the transmission speed depends on the states of the transmitted bits.
The present invention for example applies to transmissions over a single-wire bus conveying both data and a synchronization signal.
2. Discussion of the Related Art
In an open-drain (or open-collector) bus, the data conductor of the bus is, in the quiescent state, at a voltage different from ground (generally, a positive voltage). The data are coded and then transmitted by pulling of the bus to ground according to a pre-established coding enabling the receiver to decode the data.
Many communication protocols using an open-drain (or open-collector) bus are known. Be they protocols over a single-wire bus (for example, a protocol known as SWP) or over a multi-wire bus (for example, I2C-type twin-wire protocols), when several slave circuits are connected to a same bus and are capable of communicating with a same master circuit, the master circuit should send over the bus an address or an identifier of the slave circuit enabling it to recognize itself and to respond. The other slave circuits which do not recognize themselves with the address remain silent.
In usual systems, it is thus necessary for the master circuit to know the addresses of the different slave circuits, short of which several slave circuits may respond at the same time, which makes the transmission impossible to be interpreted.
In a single-wire bus protocol, a single communication conductor (in addition to a common reference or ground) is used. The signal transmitted over this bus is used both as a synchronization and data signal (and possibly as a power supply bus for the receiver).
A limitation of such a protocol is that it generally uses a single channel.